1. Field of the invention
This invention relates to turbulators on a heat transfer surfaces in a flowpath that are used to generate vortex induced turbulence to enhance heat transfer across the surface.
2. Description of Related Art
It is well known to use turbulence promoting vortex generators, often referred to as turbulators (such as fins, ribs, pins, twisted tapes, inserts, etc.), in heat transfer apparatuses and systems to increase surface heat transfer rate or performance. Heat exchanger applications that are of particular importance to the present invention have flow passages such as tubes and channels. Turbulator enhanced heat transfer devices using ribbed annular tubes have been developed to produce turbulent flows in high temperature gas cooled nuclear reactor applications. Turbulators for use in internal cooling airflow passages of hot gas turbine engine turbine blades typically are in the form of pins and ribs.
Turbulence promoting ribs have been commonly used inside the modern turbine airfoil to generate more turbulence and enhance the internal heat transfer coefficient. The rib generally has a small and square cross section (0.011.times.0.011) and a 0.111 pitch spacing. The rib can be oriented either perpendicular or angled to the flow direction. It is cast as an integral part of the airfoil. Due to the wear of the core die during the casting process, the height and shape of the rib will vary and affect its heat transfer performance. Therefore, it is important to have a surface which not only can produce effective turbulences to enhance heat transfer but also can tolerate more wear of the core die.
It is well known to use turbulator ribs that are continuous and broken and straight and angled. The use of turbulators to enhance heat transfer, however, can cause significant pressure drops across the channel or other airflow passage. It is therefore also of great importance to have a heat transfer surface that can better augment heat transfer and cause a smaller pressure drop than is conventionally available.